1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing a wiring harness using at least one set of wires (hereinafter referred to as "wiring harness set"), which can greatly reduce the lead time and production cost in the manufacturing process and can provide wiring harnesses with uniform quality.
2. Description of the Related Art
Generally, motor vehicles, including both standard and luxury motor vehicles require several hundreds or more than one thousand of separate electric wires (hereinafter referred to as simply "wires"). Much labor and time is required to manufacture a wiring harness including such a large number of wires.
FIG. 15 shows an example of the arrangement of wiring harnesses (hereinafter, also referred to as simply "harness"). The complete format of wiring harnesses for a motor vehicle includes plural harnesses formed respectively for electric parts arranged on the vehicle, e.g. an engine room harness WE, a cowl side harness WC, an instrument panel harness WI, a door harness WD, a rear side harness WR, etc. Reference symbols J1, J2, J3, . . . denote junction blocks for connecting the harnesses to each other, and the reference symbol G denotes one of a plurality of grommets for protecting (sound-proofing, water-proofing and dust-proofing) the harnesses penetrating through a panel portion such as a dashboard.
As shown in FIG. 16, each harness is composed of a trunk WO and plural branches W1, W2, W3, . . . . The terminal of each branch is connected to connectors C1, C2, C3, . . . through which the harnesses are connected to each other and to several kinds of electric devices.
The harness composed of the trunk WO and the branches W1, W2, W3, . . . includes a large number of wires. These wires include a great variety of wirings with different marks or identifiers such as different wiring diameters (standard), lengths, colors of the insulating cover and characters, symbols and stripes shown on the insulating cover. One or both ends of each wire, as shown in FIGS. 17 and 18, are connected with a crimping terminal TO and pressure welding (bonding) terminal T1. The pressing terminal includes a great number of terminals t1, t2, t3, . . . corresponding to the standards of wires and/or shapes of partner terminals. Some of the branches W1, W2, W3 . . . , as shown in FIG. 20, include wires wl, wm, and wn simply bent from the trunk WO and extracted, and separate wires wr, ws, and wt extracted from joint terminals T2 located on the trunk wires by joint (branch connection). The manner of joint includes double pressing, as shown in FIG. 19, in which two or more wires wu and wv are connected to one pressure-connection terminal t1.
With respect to the wiring harness or a great variety of wires constituting the harness, many methods and apparatuses have been proposed to automate all the processes involved from the process of cutting the wires so as to have predetermined lengths and pressure connecting the corresponding terminals thereto to the process of terminal insertion which includes mounting a connector housing to a wire end for each of the branches. (Japanese Patent Laid-Open No. 60 (Showa)-119090 and Japanese Patent Laid-Open 1 (Heisei)-313872).
However, the introduction of an automation apparatus requires a vast amount of equipment cost, and the kinds of the terminals which can be pressed by a single apparatus are limited. In addition, the fabrication of the above branch portions include processes requiring complicated processing such as the branch connection using the joint terminals T2 and double pressing. For this reason, automation of the entire process of manufacturing a wiring harness is difficult. Under the present situations, the conventional manufacturing process combines many manufacturing processes according to a batch system with only the process of making some predetermined length wires being automated.
FIG. 21 is a block diagram for explaining the process for manufacturing a wiring harness according to the conventional batch system.
The entire manufacturing process includes the processes of making predetermined length wires, classification, succeeding classification, single pressing, double pressing, joint pressing, soldering, insulation-covering, completion of preparation, terminal insertion and final processing.
(Predetermined wire length)
In this process, wires are cut to predetermined lengths, and terminal-equipped wires with one or both ends connected to a standard terminal are made. This process is performed by one or more apparatuses having means for supplying electric wires, measuring their lengths, cutting, stripping, (removal of an insulation - cover), terminal-connection and transportation. The above electric wires include terminal-free electric wires having ends with no terminals. In this process, a wide variety of electric wires having different wire diameters and lengths are made according to their class in lots (L1, L2, L3, . . .) of several tens and hundreds. Such electric wires having predetermined lengths can be made using an apparatus having well-known arrangements (Japanese Patent Publication Nos. 61-29090, 64-7468 and 3-66790).
(Classification)
In this process, the appearance of each of the lots thus made (L1, L2, L3, . . .) is examined. The wires of the lot examined are classified according to various criteria, e.g., customer, vehicle type, factory, agency, etc. In accordance with the order of making, the wires are housed or laid out to predetermined cases or wires and ordered there.
(Succeeding Classification)
The wires of each lot classified according to the agency, for example, are further classified according to the succeeding process or machine for end processing. As in the previous process, the wires classified are housed in predetermined cases or are hung in wire hangers and ordered there.
(Single Crimp)
In this process, a non-standard or a terminal having a peculiar size is crimped onto the above terminal-free electric wire or an electric wire having only one end equipped with a terminal. Namely, in this process it is difficult to apply the above apparatus of making predetermined length wires.
(Double Crimp)
In this process, a single terminal is crimped onto one end, and aligned with the terminal-free electric wires or the one end terminal equipped electric wires. The terminal used for the double crimp, as in the above single crimp, in a non-standard terminal and has a peculiar size and to which it is difficult to apply the above apparatus for making predetermined length wires, and is separately crimped. The double press is a kind of joint crimp.
(Joint Crimp)
In this process, one terminal is branch-connected to a middle or end portion of one electric wire using a joint terminal. This process reduces the number of wires used for the wiring harness, thereby reducing the volume and weight of the harness. In this process non-standard joint terminal is used so that it is difficult to apply the above apparatus for making predetermined length wires to this process. The electric wire(s) subjected to the single crimp operation or double crimp operation can be used for the joint crimp operation, as shown in FIG. 21.
(Soldering)
In this process, soldering is performed to stabilize the branch connection portion made using the joint terminal and the electrical connection portion of the terminal.
(Insulation-covering)
In this process, the above soldered portion is insulated for protection in such a manner that it is bound with an insulating tape such as a vinyl tape, applied with a one-side adhesive sheet, or mold-shaped.
(Completion of Preparation)
In this process, the complete terminal-equipped electric wire is taken out one-by-one or set-by-set, from each of the lots in which the above end processing has been completed to gather a group of wires constituting one wiring harness. One or plural sets of wires are made for each wiring harness.
(Terminal Insertion)
In this process, a group of terminals at the ends of the set of wires are inserted and locked one-by-one for each of the branches in predetermined terminal chambers of a predetermined connector housing.
(Final Process)
In this process, the set of wires thus inserted into terminals is spread on a wiring harness board and arranged according to the actual wiring format of the wiring harness. In this case, the group of wires are collectively protected by tape binding, for example, with a wire protector attached to a suitable portion (e.g., branching portions of the trunks and branches of the wires). The grommet G (FIG. 15) is mounted on the main part of the harness. The completed set of wires, after being subjected to a conduction check for each wire, presence or absence of damage in the connector housing, etc., can then be supplied to vehicle maker for use.
FIG. 22 shows the manner of actual processing to be performed in each of processes for the wires with their ends not processed (This processing will be referred to as "main process").
In the process of making predetermined length wires, in each of lots (L1, L2, L3, L4, L5, . . .), wires wl, w2-w6 necessary for a circuit at issue are made. The wire wl is equipped with both end terminals; the wires w2, w3, w5 and w6 are equipped with one end terminal, respectively, and wire w4 is equipped with no terminal. Symbols .smallcircle., .DELTA., .quadrature., .diamond. denote standard terminals which are prepared in the apparatus for performing this process.
The both-end-terminals equipped wire wl can be transferred to the process of completion of preparation. With respect to the one-end-terminal equipped w2, in the process of single pressing a different terminal .tangle-solidup. is pressed to the remaining end of the wire to form a both-end-terminals equipped wire. For the wires w3 and w4, in the process of double pressing a different terminal .tangle-soliddn. is pressed to each of their ends.
The wires w5 and w6 are jointed to the remaining end of one (w4) of the wires w3 and w4 subjected to the double pressure connection. Subsequently, the joint portion is soldered in the process of soldering, and bound with tape in the process of insulation-covering. Likewise, the wires included in the remaining lots are subjected to necessary end processing. Finally, in the process of completion of preparation, the both-end-terminal equipped electric wires wl and w2 and the joint wire w3-w4-w5-w6 are taken out one by one from each lot to assemble the set of wires.
FIGS. 23A and 23B are flow charts of the details of work in the processes of making predetermined length wires and single pressing.
Specifically, in FIG. 23A, after the processing of supplying the electric wires, measuring their length, cutting, stripping and standard terminal pressing has been completed, the wires are bundled for each lot using a rubber band. Thereafter, the bundles are curled to have a suitable size. Each curl is attached with a tag on which a product number, the number of wires and length thereof, the standard of the terminals pressed, a destination, etc. are described. The curls are hung on a wire hanger and placed in order. The wire hanger is carried to a predetermined stock position. It is stocked until the process of classification (FIG. 21).
In FIG. 23B, the group of electric wires in the lot after the classification has been completed are taken down from the wire hanger. The bundles are undone. The objects (wires) to be processed are subjected to the single crimp operation. These objects are bundled again, hung on the wire hanger and stored in the same manner as described above. Further, before the processing is advanced to the processes of double crimping, joint crimping or completion of preparation, it is confirmed whether or not there are predetermined terminals and damaged terminals. The group of wires are carried, hung on the wire hanger again and stocked.
The conventional batch system, as shown in FIG. 23A, requires, in addition to the processing of making predetermined length electric wires, many working man-hours including bundling, curling, tagging, hanging, wire hanger-carrying, etc. The single crimping as shown in FIG. 23A requires the taking down of the wire hangers, bundle-undoing before the processing, and requires, after the processing, more working man-hours composed of the bundling, hanging, stocking, confirming, classifying according to process/machine, wire carrying and wire hanger-carrying. This situation also applies in the processes of double crimping, joint crimping, soldering and insulation-covering.
Thus, the method of manufacturing a wiring harness according to the conventional batch system has the following problems to be solved:
1. Many operations, including predetermined length wire making to terminal insertion, associated with the pressing process must be repeated with each pressing process, results in great wasteful effort.
2. There is a time delay due to stocking between the adjacent processes from the process of predetermined length wire making to the process of terminal insertion. So, this requires a vast stocking space, and also results in a long lead time from the making of the predetermined length wire to the terminal insertion including the accompanying operations.
3. Each of the processes, from the making of the predetermined length wire to the terminal insertion, is an individual operation so that there is less correlation among the processes. Therefore, it takes a long time for workers to understand the entire process and master it.
4. An operation, such as wire hanger carrying, must be performed whenever one process is shifted to the succeeding process. For this reason, inferior goods resulting from tangling of the terminals crimped and stamping by the wire hanger may be made for each lot.
5. Some inferior goods are inevitably generated in the processes of single press, double press processing and joint press after the process of making predetermined length wires. In this case, the percentage of inferior goods is different for each process. A correct number of wires cannot be prepared for the set of wires which are formed by collecting the processed wires from each lot. In order to compensate for the shortage, a redundant number of wires must be prepared for each lot.
6. Out of the set of wires prepared, it is not easy to discriminate those lots having either a surplus or shortage in the number of wires. Since there are a great number of terminals and connector housings, in the process of terminal insertion, false insertion of the terminals is inevitable.
7. Because of the existence of the above problems, in the entire conventional batch system, it is difficult to assure the wiring harness with stable quality equal to when an automated device is used.